Circuit for controlling a selector



y 3. 1956 R. M. M. OBERMAN CIRCUIT FOR CONTROLLING A SELECTOR 2 Sheets-Sheer Filed Oct. 1, 1951 Fig.1

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Filed Oct. 1, 1951 INVENTOR. R m? M. N. Che-(won BY MQQAQQLL 9 CIRCUIT FDR CONTROLLING A SELECTOR Roelof M. M. Olierman, The Hague, Netherlands Application Uctober 1, 1951, Serial No. 249,049 In Netherlands March 26, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires March 26, 1966 19 Claims. (Cl. 179-18) The invention relates to a new and useful improvement in automatic switching systems such as telephone systems, in particular applicable to rotary systems in which the outlets of a selector each have a characteristic electrical marking.

The present application is a continuation-in-part of my co-pending application Serial No. 767,528, filed July 30, 1947.

It is an object of the present invention to provide a switching system with a safe operation.

It is another object of the present invention to afford a rapid performance of the positioning of the selectors, thus reducing the necessary equipment.

It is a further object of the present invention to reduce the current consumption for marking.

It is still another object of the present invention to prevent disturbing clicks from arising in an existing con nection between two subscribers if one subscriber is called but found busy.

A telecommunication system according to the present invention comprises in its broadest aspects a selector having a plurality of outlets, a register positioning the selector, the register registering digits, means for marking the outlets of the selector with different potentials, respectively, means for comparing the marking potentials of the outlets of the selector with potentials corresponding to the registered digits, and means in the selector for operating the outlet marking means. Preferably, the operating means connect the outlet marking means to the register. Preferably, means for operating the selector are controlled by the means operating said outlet marking means.

A preferred embodiment of the invention comprises in combination, a selector, a register positioning the selector, means operated by the register for seizing the selector, and means for switching through the selector, the switching-through means being controlled by the seizing means upon release thereof by the register. Preferably, means are provided for operating the selector controlled by the seizing means and the switching-through means.

A preferred embodiment of the invention comprises a selector having a plurality of outlets, a register positioning the selector, a first contact bank and a second contact bank in the selector, a first and a second wiper engaging the first and second contact banks, respectively, a plurality of potentiometers associated with the outlets, respectively, and each having a first and a second resistor, the first resistors being connected to the first contact bank of the selector, and a current source having one terminal connected to the second resistors, the junctions of the first and the second resistors being connected to the second contact bank, the first wiper being connected to the other terminal of the current source.

Preferably, a telecommunication system according to the present invention comprises a selector, a register for positioning the selector, a relay for seizing the selector, a relay for switching through the selector, the seizing and switching-through relays being connected to each other nited States Patent e CC in the circuit of the selector, a current source having one terminal connected to one terminal of the seizing relay, releasable means in the register for connecting the other terminal of the seizing relay to the other terminal of the current source so as to operate the seizing relay, means controlled by the register for connecting the other terminal of the current source to the switching-through relay for operating the switching-through relay and the seizing relay in series upon release of the releasable means in the register. Preferably, such a system has a plurality of potentiometers having each a first resistor and a second resistor and being associated, respectively, with the outlets of the selector, a contact bank and a wiper engaging the contact bank in the selector, means for connecting the wiper to the register, the current source having the one terminal thereof connected to the first resistors, a contact controlled by the seizing relay for connecting the other terminal of the current source to the second resistors upon energization of the seizing relay, the junctions of the first and the second resistors being connected to the contact bank, means for registering by the register a plurality of potentials corresponding, respectively, to digits, and means in the register for comparing the potentials supplied by the potentiometers with the potentials registered by the register.

A preferred embodiment of the present invention comprises in combination a selector having a plurality of outlets and a zero position, a register positioning the selector, means for operating the selector under the control of the register, a busy-testing device in the register for discriminating the busy and free condition of a selected outlet of the selector, means controlled by the busy-testing device for switching through the selector to the selected outlet on testing the same as free, and means in the register controlled by the busy-testing device for preventing the means for switching-through from operating on testing the selected outlet as busy and directing the selector to the zero position thereof.

Preferably a telecommunication system according to the present invention comprises a selector having a plurality of outlets and a zero position, a register positioning the selector, the register being adapted to register digits, marking means for marking the outlets and the zero position of the selector, means for comparing the marking of the outlets of the selector with the digits registered by the register, a busy-testing device in the register for discriminating the busy and free condition of a selected outlet of the selector, means controlled by the comparing means for operating the selector, a relay switching through the circuit of the selector controlled by the busytesting device and energizing the same on testing a selected outlet as free, and means in the register controlled by the busy-testing device for preventing the switchingthrough relay from operating on testing the selected outlet as busy and for directing the selector to the zero position thereof.

A preferred embodiment of the present invention comprises a selector having a plurality of outlets, a register positioning the selector, a first contact bank and a second contact bank in the selector, a first and a second wiper engaging the first and second contact banks, respectively, a plurality of potentiometers in the circuit of the selector and each having a first resistor and a second resistor for each outlet and the zero position of the selector, a current source having one terminal connected to the first resistors, a relay for seizing the selector, the seizing relay having one terminal connected to the one terminal of the current source, a starting relay in the register for connecting the other terminal of the current source to the seizing relay and energizing the same, the seizing relay having a contact connecting the other terminal of the current source to the second resistors, the first contact bank being connected to the junctions of the first and the second resistors, a plurality of potentiometers in the register, means in the register for selecting one of the potentiometers in the register for each digit, respectively, means for comparing the potential supplied by the selected one of the potentiometers associated with the selector with the potential supplied by the selected one of the potentiometers in the register, a busy-testing device for discriminating the busy and free condition of an outlet of the selector, the seizing relay connecting the second wiper of the busy-testing device, and a magnet for rota. the wipers through the contact banks, respectively, the magnet being controlled by the comparing means. Preferably, the potentiometers in the register include a potentiometer corresponding to the marking of the zero position of the selector, the busy-testing device connecting the otentiometer corresponding to the marking of the zero position to the potential comparing means. Preferably, a signal switch is arranged in the register and controlled by the potential comparing means and the busy-testing device. Preferably, a relay for switching through the selector is controlled by the sequence switch and the busy-testing device, this control being effected by a starting relay operated by a control relay being controlled by the sequence switch and the busy-testing device.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itsel however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 shows a register and a group selector under the control of said register which is only shown insofar as necessary for understanding the invention; and

Fig. 2 which should be placed at the right hand side of Fig. 1, shows diagrammatically a final select r with two subscribers connected thereto, and a part of a line finder.

The register which is shown in Fig. l comprises a sequence switch which is indicated by the contacts pz and the magnet Mrs thereof. This sequence switch may be the switch controlling the various stages of building up a wanted. connection to a subscriber, but it may also include the switch controlling the reception of the digits corresponding to a Wanted subscriber and the building up of the pertinent connection. The reference numerals indicating the closure of the contacts of the sequence switch are only an indication in which succession said contacts are closed.

The marking switches, MSC for the hundreds digit, MSX for the tens and M51 for the units, in the register are positioned according to the digits issued by the calling party in a way not forming an essential element of the present invention and well-known in the art. The contact banks of the marking switches have each a plurality of contacts which are connected at tappings of a series potentiometer R31. in Fig. 1 this is shown symbolically by the connection of one single contact out of the relevant contact banks to any tapping point of said series potentiometer R31. It should be understood that the other contacts are also connected to the series potentiometer. The brushes engaging the contact banks of said marking switches can be connected by means of the contacts q, r and s of the sequence switch to a square marked NW.

The square NW diagrammatically represents a voltage comparison device as for instance set forth in my copending patent applications Serial No. 25,108, filed May 5, 1948, now Patent No. 2,654,837, and Serial No. 111,394, filed August 20, 1949, now Patent No. 2,577,147. Such device consists of a tube arrangement having an anode circuit in which a test relay T is provided which is energized when the bias of the tube arrangement is approximately zero.

The square ET in the register and the relay D connected thereto represents a busy device for testing whether a wanted outlet is busy or free. The busy-testing device may also be a tube arrangement like the comparison device NW, or merely consist of a relay such as D.

The register further comprises a starting relay SR, a control relay CR and an auxiliary relay E controlling contacts sr sr cr cr cr and e e respectively. Contacts t and d are controlled by the relays T and D, respectively.

The regist r is connected over a selector S which may he a cord "cider, or, if desired, a group selector, to a group selected GS. The group selector GS comprises in its circuit a seizing relay AG controlling contacts ag ag and a switching-through relay BG controlling contacts bg bg The wiper assembly of the group selector GS carries wipers ("we and is operated by means of a magnet MG. A potentiometer R11 supplies the marking potential which is characterizing for the group selector GS, whereas the potentiometer R23 supplies the marking potcntial for the zero position of the finder switch S.

The contact banks of the group selector GS which are engaged by said wipers have access to a plurality of final selectors one of which is shown in Fig. 2 and denoted by The final selector has a seizing relay AF and a switching-through relay BF controlling contacts afl-af and bf -bf Two subscribers stations are indicated by the squares X and Z.

The operation of the system is as follows when assumed that digits corresponding to the subscribers sets X and Z are registered by the marking switches:

The sequence switch is operated and moved to position 1 when the digits for selecting a wanted subscriber have been registered by the marking switches MSC, MSX and MS! in the register. A circuit for the starting relay SR is now completed from ground over the closed contact p of the sequence switch, contact 01- and the winding of relay SR to battery and ground.

The sequence switch will now move on while the positioning of the cordfinder indicated by the selecting switch S, takes place. The sequence switch reaches position 4 in which the group selector GS has to be positioned.

By means of contact sr ground is applied to the seizing relay AG of the group selector GS in the circuit ground in the register over contact sr the a-wiper and contact bank of the selector S, contact bg the winding of relay AG to battery and ground so that the seizing relay AG is energized. By means of contact ag a circuit for the busy test of the outlets of group selector GS is prepared. Contact'ag prepares a holding circuit for relay B6 in series with relay AG from ground in the register over the closed contact v of the sequence switch to the d-wiper and bank of the selector S, contact ag the winding of switching-through relay BG. However, owing to the ground potential supplied over contact sr on the a-Wire, relay EG does not yet operate.

Contact rig on the other hand disconnects ground in the register from the left-hand terminal of the potentiometer R11 whereas contact ag disconnects the tapping point or" said potentiometer from the e-wire to which the characteristic marking potential for the pertinent group selectors was applied, and instead connects the coupling magnet MG of the group selector GS via the e-wire to the register. The operating circuit for the magnet MG leads from ground over the winding of magnet MG, hack contact bg front contact ag e-banh and wiper of the selector S, and in the register over front contact sr back contact t, back contact cr and resistor R36 to battery and ground.

As it has been assumed that the group. selector GS selects the final selector PS shown in Fig. 2, the marking switch MSC takes on? from the potentiometer R31 a potential which corresponds to the potential occurring at the tapping point of a marking potentiometer represented by the resistors R1 and R2. A characteristic potential occurs at the tapping point of said marking potentiometer as soon as the d-wiper of group selector GS touches the shown outlet, thereby applying ground over front-contact ag at the left-hand terminal of resistor R1, which makes part of said marking potentiometer. There is no real tapping point unless contact af remains in its back-position, thereby interconnecting resistors R1 and R2. Then said tapping point leads over back-contact it At the same time the e-wiper of group selector GS touches the shown outlet and transfers said characsteristic potential via back-contact af e-bank and -wiper of group selector GS, front contact ag, back contact bg b-bank and wiper of the positioned selector S to the voltage comparing device NW. At this time the potential derived by the marking switch MSC from the potentiometer R31 and the transferred potential will be substantially the same so that relay T is operated. The operating circuit for the magnet MG is then interrupted at contact r so that the group selector GS stops.

The busy-testing device BT causes relay D either to operate or not dependent on whether the seized outlet is busy or free, respectively. When the selector to which the subscriber is connected is not just seized by another register over the multiple, ground potential is received over resistor R8, back contact a), the c-bank and wiper of the group selector GS, front contact ag the c-bank and wiper of the selector S by the busy test device BT to which the relay D does not respond, so that the armature d remains in the shown position. A circuit for the stepping magnet M'ss of the sequence switch is closed from ground over the Winding of the magnet Mss, back contact d, front contact 1', back contact cr resistor R36 to battery and ground in which the magnet Mss operates after the free condition has been ascertained.

If however, the wanted outlet is engaged by another calling register, the marking potential normally supplied via back-contact af is replaced by ground via magnet MF and front-contact a In consequence relay T does not operate when passing the wanted outlet, so that the magnet MG keeps operated in its circuit described hereinbefore, whilst the group selector GS moves on. When for some reason, for instance when a selector circuit is used in which the marking circuit is not interrupted, or the marking potential remains owing to a failure, an outlet is found which is tested busy, so that both the relays T and D are energized, the operating winding of the auxiliary relay E receives current in the circuit; ground over the lower winding of relay E, contact y of the sequence switch in position 4, front contact a, front contact I, back contact cr register R36 to battery and ground. Then relay E holds itself via make contact e and contact x of the sequence switch, thereby energizing magnet Mss, until the sequence switch reaches position 12.

The magnet lvlss of the sequence switch can be energized in two ways either for a free outlet over the back contact d of relay D in the above-explained circuit in which case only one step is made or for a busy outlet over contact x of the sequence switch and the front contact e of relay E in which case the sequence switch is moved to position 12 in which the potential BM is connected to the comparison device NW by means of contact 11 of the sequence switch. The potential BM is different from the marking potentials and corresponds to the potential Vb supplied in the zero position of the switches and which is derived from the potentiometers R23, R13, and R3 for the selector switch S, the group selector GS, and the final selector FS, respectively. When the potential BM is connected to the comparison device NW, the test relay T remains unoperated and the operating ircuit for the magnet of the relevant selector is consequently kept closed by means of the contact 1 to that the selector moves on until reaching its zero position, in which both the potentials Vb and that derived by tapping 6 point BM, match, causing the operation of relay T and in consequence the interruption of the operating circuit of magnet MG, which stops.

When the sequence switch only makes one step, the wanted outlet being free, the relay E is not energized and contact e remains closed so that in position 4 /2 of the sequence switch an energization circuit for the upper winding of the control relay CR is closed by contact w so that the relay CR is now connected over contact cr to a ground potential on the e-wire so that the magnet MG cannot be operated by another register. Contact c1- ensures that no current from the register shown in the drawings can restart the magnet MG which would result in a wrong position. Contact cr interrupts the energization circuit for relay SR, which thereupon releases its armatures sr and sr The release of armature sr breaks the circuit for the seizing relay AG which, however, does not release because a holding circuit was prepared in series with the switching through relay BG over contact v of the sequence switch, d-wiper and -contact bank of selector switch S and front contact ag Relays AG and BG are then energized in the circuit; ground in register, contact 1/ of the sequence switch, d-wiper and associated bank switch S, front contact ag relay BG, relay AG, battery, ground. Upon the energization of relay E6 the circuit is switched through to the group selector GS and to the circuit of the final selector FS. Contact bg disconnects the junction of the relays AG and BG from the register and connects the junction of the seizing relay AF and switching-through relay BF to the circuit so that the same are brought under the control of the register. Contact bg disconnects the comparison device NW from the marking circuit of the positioned selector GS and connects the same to the marking circuit of the final selector FS. At contact bg the control circuit of the register for the magnets of the selectors is switched from magnet MG of the group selector GS to the magnet MP of the final selector FS via e-wiper and -bank of group selector GS and contact af The potential Vb, which marked the zero position of group selector GS, is removed now as break contact lag interrupts the current supply of marking potentiometer R13, thus moreover limiting the current consumption whilst protecting said marking potentiometer against overload, which might occur if the same should be put into circuit permanently.

In the meantime the sequence switch in the register moves on to position 5 and thus de-energizes by its contact w the control relay CR. Relay SR is operated again over contact p of the sequence switch and back contact cr While comparison potential over the marking switch MSX is connected to the voltage comparison device NW over the contact r of the sequence switch which is now closed. Contact sr is closed upon the re-energization of relay SR so that a circuit is closed from ground, over the a-wire, a-wiper and bank of the selector S, front contact bg a-wiper and bank of the group selector GS, back contact by and relay AF, and battery to ground in which circuit relay AF is energized and attracts the armatures ai -af thereof. Contact af connects the busy testing device BT to the outlets of the final selector FS. Contact af prepares a holding circuit for relay AF in series with the switching-through relay BF, which starts at ground in the preceding selecting stage and proceeds over front contact ag (which was closed for originating the marking potentials at the junction of resistors R1 and R2), d-wiper and bank of group selector GS, resistor R1, front contact af relay BF to the junction with relay AF, to which junction for the time being a ground potential is applied via back control bf so that relay BF is not energized yet. At contact a the marking potentiometer composed of resistors R1 and R2 is disconnected from the e-wire while at contact af the magnet MP of the final selector FS is connected to the register, the circuit including ground, the magnet MF, front contact af e-bank and wiper of the group selector GS, front contact bg front contact ag e-bank and wiper ofthe selector S, front contact sr back contact t, back contact cr resistor R36, battery, and ground. Therefore the magnet MP is controlled by the contact z of the relay T connected to the voltage comparison device NW. It will be clear to anyone skilled in the art that contacts af and a may be combined to a single changeover contact device.

Contact applies the marking potentials occurring on the e-bank of the final selector PS, at the comparison device NW, while contact af closes the supply circuit for the marking potentiometer R3. Only three of the outlets of the final selector F8 are shown connected at tappings of potentiometer R3 in Fig. 2 in order to keep that figure more surveyable. The final selector PS will first be positioned according to the tens digit which is represented as a comparison potential on the marking switch MSX which for instance corresponds to the marking potential Vx applied at one of the outlets shown in Fig. 2. The final selector FS thus moves until the desired tens position is reached.

Then relay T operates. Since contact 3 of the sequence switch in position 5 interrupts the operating circuit of relay CR relay SR is kept operated via backcontact er In consequence front-contact sr prevents relay BF from being energized. Since contact z of the sequence switch shunts in position 5, back-contact d the magnet Mss drives the sequence switch to its position 6, independent of whether the outlet being tested is busy or not, in a circuit; battery, resistor R36, back-contact cr front contact t, contact z of the sequence switch and magnet Mss. In position 6 contact s of the sequence switch applies the wanted unit digit at the comparison device NW, which unit digit is derived from marking switch MSI. In general relay T then deenergizes, so that the sequence switch is kept in position 6, whereas the magnet MP of the final selector FS is operated in the circuit traced hereinbefore, until the wanted outlet is found. In case the unit digit amounts to zero further movement of the final selector is supressed as the same is already positioned by connecting the zero contact of marking switch MSI with the wiper of the tensdigit switch MSX. Suppose that the position of the unit-switch MSI corresponds with a subscribers station Z.

When the wanted outlet is reached the final selector FS is stopped owing to the operation of relay T and the busy test device BT ascertains the busy condition of the outlet. If the outlet is seized and the subscriber is busy a contact corresponding to b of the multiple supplies battery potential over a resistor R7, the d-wiper and bank of a final selector PS to the multiplied c-banks of the final selectors FS. In such case relay D operates since a voltage is applied at the busy-testing device BT via the c-wiper of final selector FS, front-contact af c-bank and Wiper of group selector GS, front-contact ag and contactbank and wiper of selecting switch S, which voltage substantially differs from ground potential. Also relay T operates as both potentials, that supplied by the unit switch MSI and that supplied by marking potentiometer R3, match. In consequence relay E operates in the circuit: battery, resistor R36, back-contact cr front'contacts t and d, contact y of the sequence switch in position 6, lower winding of relay E, ground relay E holds itself via contact x of the sequence switch and its contact 2 the magnet Mss being operated too, so that the sequence switch moves on to position 12, in which the potential BM is applied via contact u of the sequence switch to the comparison device NW. It should be noted that contact e prevents relay CR from being energized in position 6 of the sequence switch. When the potential BM is applied relay T is de-energized and thus completes the circuit for magnet MP again which moves the final selector FS into the zero position thereof in which thefinal selector FS is stopped. In the zero position the sequence switch again makes a step thus initiating the release of the register in a well-known manner. In case the subscriber is free the busy testing device BT finds ground potential via resistor R5, c-bank and wiper of final selector FS, front-contact af c-bank and wiper of group selector GS, front-contactag and c-bank and wiper of selector switch S. In consequence relay D does not operate though relay T does thus causing the operation of magnet Mss in the circuit: battery, resistor R36, back-contact cr front-contact t, back-contact d, magnet Mss, ground. The sequence switch reaches position 6 /2, in which relay CR is operated via back-contact e and contact w of the sequence switch. Contact cr breaks the energizing circuit of the magnets Mss and MF, thus preventing the same from operating, whereas contact cr breaks the operating circuit of relay SR, which is deenergized. Contact sr removes ground from the junction of the windings of relays AF and BF, so that said relays energize in their holding circuit: ground, front-contact ag d-wiper and bank of group selector GS, resistor R1, front-contact af windings of relays BF and AF, battery. The current supply through marking potentiometer R3 is broken by contact bf, whereas front-contact bf applies battery via resistor R7 at the d-wiper and bank of the engaged final selector PS.

The relevant outlets of the cand d-banks of F8 are marked now by potentials, which differ from ground potential, so that they are marked busy, preventing other final selectors from being stopped at the relevant outlet. Contacts bf and bi finally switch the aand b-wires through.

Fig. 2 shows part of a line finder LP of which the d-wiper and bank perform the same function as the d-wiper and bank of the final selector FS. Thus in case a subscriber has been busied by the line finder LF battery potential is supplied over resistor R9, front contact bl of the switching through relay (not shown) of the linefinder LF, d-wiper and bank of the linefinder LF to the line circuit of the relevant subscriber.

By making use of a system as explained hereinabove in which the speech wires of the wanted outlet to which a subscriber is connected are disconnected from the circuit before switching through, a highly undesirable click is avoided which would otherwise occur at the subscribers station. Such a click might even be a prolonged crackling which makes a telephone conversation impossible.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of telephone systems differing from the types described above.

While the invention has been illustrated and described as embodied in a rotary system having a selector the outlets of which are electrically marked, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; a first contact bank and a second contact bank in said selector; a first and a second wiper engaging said first and second contact banks, respectively; a plurality of voltage dividers associated with said outassassin lets, respectively, and each of said voltage dividers having a first and a second resistor, said first resistors being connected to said first contact bank of said selector; and a current source having one terminal connected to said second resistors, the junctions of said first and said second resistors being connected to said second contact bank, said first wiper being connected to the other terminal of said current source.

2. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; a first contact bank and second contact bank in said selector; a first and a second wiper engaging said first and second contact banks, respectively; a plurality of voltage dividers associated with said outlets, respectively, and each of said voltage dividers having a first and a second resistor, said first resistors being connected to said first contact bank of said selector; a current source having one terminal connected to said second resistors, the junctions of said first and said second resistors being connected to said second contact bank, said first Wiper being connected to the other terminal of said current source; means for registering by said register a plurality of potentials corresponding, respectively, to digits; means in said register for comparing the potentials supplied by said voltage dividers with the potentials registered by said register; and means controlled by said potential comparing means for controlling the positioning of said selector.

3. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; a first contact bank and a second contact bank in said selector; a first and a second wiper engaging said first and second contact banks, respectively; a plurality of voltage divider networks associated with said outlets, respectively, and each of said networks having a first and a second resistor, said first resistors being connected to said first contact bank of said selector; a current source having one terminal connected to said second resistors, the junctions of said first and said second resistors being connected to said second contact bank, said first wiper being connected to the other terminal or" said current source; a relay for seizing said selector, said relay being controlled by said selector; and a relay for switching through said selector, said switching-through relay being controlled by said register.

4. In a telecommunication system, in combination, a selector; a register for positioning said selector; a seizing relay for connecting said selector to said register; a relay for switching through said selector, said seizing and switching-through relays being connected to each other in the circuit of said selector; a current source having one terminal connected to one terminal of said seizing relay; releasable means in said register for connecting the other terminal of said seizing relay to the other terminal of said current source so as to operate said seizing relay; means controlled by said register for connecting the other terminal of said current source to said switching-through relay for operating said switching-through relay and said seizing relay in series upon release of said releasable means in said register.

5. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; a seizing relay for connecting said selector to said register; a relay for switching through said selector, said seizing and switching-through relays being connected to each other in the circuit of said selector; a current source having one terminal connected to one terminal of said seizing relay; releasable means in said register for connecting the other terminal of said seizing relay to the other terminal of said current source so as to operate said seizing relay; means controlled by said register for connecting the other terminal of said current source to said switching-through relay for operating said switch-through relay and said seizing relay in series upon release of said releasable means in said it) register; a plurality of voltage divider networks, each of said networks having a first resistor and a second resistor; a contact bank and a wiper engaging said con tact bank in said selector; means for connecting said wiper to said register, said current source having said one terminal thereof connected to said first resistors; a contact controlled by said seizing relay for connecting said other terminal of said current source to said second resistors upon energization of said seizing relay, the junctions of said first and said second resistors being connected to said contact bank; means for registering by said register a plurality of potentials corresponding, respectively, to digits; and means in said register for comparing the potentials supplied by said voltage divider network with the potentials registered by said register.

6. In a telecommunication system, in combination, a selector; a register for positioning said selector; a seizing relay for connecting said selector to said register; a relay for switching through said selector, said seizing and switching-through relays being connected to each other in the circuit of said selector; a current source having one terminal connected to one terminal of said seizing relay; releasable means in said register for connecting the other terminal of said seizing relay to the other terminal of said current source so as to operate said seizing relay; means controlled by said register for connecting the other terminal of said current source to said switching-through relay for operating said switching-through relay and said seizing relay in series upon release of said releasable means in said register; and means for operating said selector, said selector operating means being controlled by said seizing relay and said register.

7. In a telecommunication system, in combination, a selector; a register for positioning said selector; a seizing relay for connecting said selector to said register; a relay for switching through said selector, said seizing and switching-through relays being connected to each other in the circuit of said selector; a current source having one terminal connected to one terminal of said seizing relay; releasable means in said register for connecting the other terminal of said seizing relay to the other terminal of said current source so as to operate said seizing relay; means controlled by said register for connecting the other terminal of said current source to said switchingthrough relay for operating said switching-through relay and said seizing relay in series upon release of said releasable means in said register; a busy testing device in said register for testing the busy condition of an outlet of said selector; and a contact of said seizing relay for connecting said busy testing device to the outlets of said selector.

8. In a telecommuncation system, in combination, a selector; a register for positioning said selector; a seizing relay for connecting said selector to said register; a relay for switching through said selector, said seizing and switching-through relays being connected to each other in the circuit of said selector; a current source having one terminal connected to one terminal of said seizing relay; releasable means in said register for connecting the other terminal of said seizing relay to the other terminal of said current source so as to operate said seizing relay; means controlled by said register for connecting the other terminal of said current source to said switchingthrough relay for operating said switching-through relay and said seizing relay in series upon release of said releasable means in said register, said switching-through relay busying an outlet of said selector.

9. In a telecommunication system, in combination, a selector having a plurality of outlets and a zero position; a register for positioning said selector; means for operating said selector under the control of said register; a busy-testing device in said register for discriminating the busy and free condition of a selected outlet of said selector; means controlled by said busy-testing device for switching-through said selector to said selected outlet on testing the same as free; and means in said register controlled by said busy-testing device for preventing said means for switching-through from operating on testing said selected outlet as busy and directing said selector to the zero position thereof.

10. In a telecommunication system, in combination, a selector having a plurality of outlets and a zero position; a register for positioning said selector; means for operating said selector under the control of said register; a busy-testing device in said register for discriminating the busy and free condition of a selected outlet of said selector; means controlled by said busy-testing device for switching-through said selector to said selected outlet on testing the same as free; means in said register controlled by said busy-testing device for preventing said means for switching-through from operating on testing said selected outlet as busy and directing said selector to the zero position thereof; and means for releasing said register after the zero position of said selector has been reached.

11. In a telecommunication system, in combination, a selector having a plurality of outlets and a zero position; a register for positioning said selector, said register being adapted to register digits; marking means for marking said outlets and said zero position of said selector; means for comparing the marking of said outlets of said selector with the digits registered by said register; a busy-testing device in said register for discriminating the busy and free condition of a selected outlet of said selector; means controlled by said comparing means for Operating Said selector; a relay switching-through said circuit of said selector controlled by said busy-testing device and energizing the same on testing a selected outlet as free; and means in said register controlled by said busy-testing device for preventing said switching-through relay from operating on testing said selected outlet as busy and for directing said selector to the zero position thereof.

12. In a telecommunication system, in combination, a selector having a plurality of outlets and a zero position; a register for positioning said selector, said register being adapted to register digits; marking means for marking said outlets and said zero position of said selector; means for comparing the marking of said outlets of said selector with the digits registered by said register; a busy-testing device in said register for discriminating the busy and free condition of a selected outlet of said selector; means controlled by said comparing means for operating said selector; a relay switching-through said circuit of said selector controlled by said busy-testing device and energizing the same on testing a selected outlet as free; means in said register controlled by said busy-testing device for preventing said switching-through relay from operating on testing said selected outlet as busy and for directing said selector to the zero position thereof; and means in said register controlled by said busy-testing device when testing an outlet as busy for rendering said comparing means responsive to the marking of the zero position of said selector.

13. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; a first contact bank and a second contact bank on said selector; a first and a second wiper engaging said first and second contact banks, respectively; a plurality of voltage divider networks in the circuit of said selector, each network having a first resistor and a second resistor for each outlet and the Zero position of said selector; a current source having one terminal connected to said first resistors; a seizing relay for connecting said selector to register, said seizing relay having one terminal connected to said one terminal of said current source; a starting relay in said register for connecting the other terminal. of said current source to said seizing relay and energizing the same, said seizing relay having a contact connecting said other terminal of said current source to said second resistors; said first contact bank being connected to the junctions of said first and said second resistors; a plurality of voltage divider networks in said register; means in said register for selecting one of said voltage dividers in said register for each digit, respectively; means for comparing the potential supplied by the selected one of said networks connected to said selector with the potential supplied by the selected one of said voltage dividers in said register; a busy-testing device for discriminating the busy and free condition of an Outlet of said selector, said seizing relay connecting said second wiper to said busy-testing device; and a magnet for rotating said wipers through said contact banks, respectively, said magnet being controlled by sai comparing means.

14. in a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; a first contact bank and a second contact bank on said selector; a first and a second wiper engaging said first and second contact banks, respectively; a plurality of voltage divider networks in the circuit or said selector, each network having a first resistor and a second resistor of each outlet and the zero position of said selector; a current source having one terminal connected to said first resistors; a seizing relay for connecting said selector to said register, said seizing relay having one terminal connected to said one terminal of said current source; a starting relay in said register for connecting the other terminal of said current source to said seizing relay and energizing the same, said seizing relay having a contact connecting said other terminal of said current source to said second resistors, said first contact bank being connected to the junctions of said first and said second resistors; a plurality of voltage divider networks in said register; means in said register for selecting one of said voltage dividers in said register for each digit, respectively; means for comparing the potential supplied by the selected one of said networks connected to said selector with the potential supplied by the selected one of said voltage dividers in said register; a busy-testing device for discriminating the busy and free condition of an outlet of said selector, said seizing relay connecting said second wiper to said busy-testing device; and a magnet for rotating said wipers through said contact banks, respectively, said magnet being controlled by said comparing means, said potentiometers in said register including a potentiometer 7 corresponding to the marking of the zero position of said selector, said busy-testing device connecting said potentiometer corresponding to the marking of the zero position to said comparing means.

15. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; a first contact bank and a second contact bank on said selector; a first and a second wiper engaging said first and second contact banks, respectively; a plurality of voltage divider networks in the circuit of said selector, each network having a first resistor and a second resistor for each outlet and the zero position of said selector; a current source having one terminal connected to said first resistors; a seizing relay for connecting said selector to said register, said seizing relay having one terminal connected to said one terminal of said current source; a starting relay in said register for connecting the other terminal of said current source to said seizing relay and energizing the same, said seizing relay having a contact connecting said other terminal of said current source to said second resistors, said first contact bank being connected to the junctions of said first and said second resistors; a plurality of voltage divider networks in said regis ter; means in said register for selecting one of said voltage dividers in said register for each digit, respectively; means for comparing the potential supplied by the selected one of said networks connected to said selector with the potential supplied by the selected one of said voltage dividers in said register; a busy-testing device for discriminating the busy and free condition of an outlet of said selector, said seizing relay connecting said second wiper to said busy-testing device; a magnet for rotating said wipers through said contact banks, respectively, said magnet being controlled by said comparing means; and a sequence switch in said register controlled by said comparing means and said busy-testing device.

16. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; a first contact bank and a second contact bank on said selector; a first and a second wiper engaging said first and second contact banks, respectively; a plurality of voltage divider networks in the circuit of said selector, each network having a first resistor and a second resistor for each outlet and the zero position of said selector; a current source having one terminal connected to said first resistors; a seizing relay for connecting said selector to said register, said seizing relay having one terminal connected to said one terminal of said current source; a starting relay in said register for connecting the other terminal of said current source to said seizing relay and energizing the same, said seizing relay having a contact connecting said other terminal of said current source to said second resistors, said first contact bank being connected to the junctions of said first and said second resistors; a plurality of voltage divider networks in said register; means in said register for selecting one of said voltage dividers in said register for each digit, respectively; means for comparing the potential supplied by the selected one of said networks connected to said selector with the potential supplied by the selected one of said voltage dividers in said register; a busy-testing device for discriminating the busy and free condition of an outlet of said selector, said seizing relay connecting said second wiper to said busy-testing device; a magnet for rotating said wiper through said contact banks, respectively, said magnet being controlled by said comparing means; a sequence switch in said register controlled by said comparing means and said busy-testing device; and a relay for switching through said selector, said switching-through relay in said selector circuit being controlled by said sequence switch and said busy-testing device.

17. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; a first contact bank and a second contact bank on said selector; a first and a second wiper engaging said first and second contact banks, respectively; a plurality of voltage divider networks in the circuit of said selector, each network having a first resistor and a second resistor for each outlet and the Zero position of said selector; a current source having one terminal connected to said first resistors; a seizing relay for connecting said selector to said register, said seizing relay having one terminal connected to said one terminal of said current source; a starting relay in said register for connecting the other terminal of said current source to said seizing relay and energizing the same, said seizing relay having a contact connecting said other terminal of said current source to said second resistors, said first contact bank being connected to the junctions of said first and said second resistors; a plurality of voltage divider networks in said register; means in said register for selecting one of said voltage dividers in said register for each digit, respectively; means for comparing the potential supplied by the selected one of said networks connected to said selector with the potential supplied by the selected one of said voltage dividers in said register; a busy-testing device for discriminating the busy and free condition of an outlet of said selector, said seizing relay connecting said second wiper to said busy-testing device; a magnet for rotating said wiper through said contact banks, respectively, said magnet being controlled by said comparing means; a sequence switch in said register controlled by said comparing means and said busy-testing device; a relay switching through said selector circuit, said switching-through relay being controlled by said starting relay; and a control relay in said register for operating said starting relay, said control relay being controlled by said sequence switch and said busy-testing device.

18. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; registering means in said register for registering digits; means for marking said outlets of said selector with difierent potentials, respectively, each of said marking means including a separate potential source for each of said different potentials; means for comparing the marking potentials of said outlets of said selector with potentials corresponding to the registered digits; and means in said selector for operating said outlet marking means.

19. In a telecommunication system, in combination, a selector having a plurality of outlets; a register for positioning said selector; registering means in said register for registering digits; means for marking said outlets of said selector with different potentials, respectively, each of said marking means including a separate potential source for each of said different potentials; means for comparing the marking potentials of said outlets of said selector with potentials corresponding to the registered digits; and means in said selector for operating said outlet marking means, said operating means connecting said outlet marking means to said register.

References Cited in the file of this patent UNITED STATES PATENTS Re. 22,861 Deakin et al. Apr. 8, 1947 2,547,043 Pouliart Apr. 3, 1951 2,559,601 Deakin July 10, 1951 2,570,214 Deakin Oct. 9, 1951 2,696,525 Deakin Dec. 7, 1954 

